MICROSCOPIC OBJECTS. 77 



the Gooseberr}\ In the common Borage and the Anchusa 

 angustifolia, the base has a bulb, hke the spines of an 

 Echinus. Examples of the principal varieties of hairs will 

 be found in the plants named in the list. 



Volatile Oil in Leaves. — The leaves of the Sage, 

 Black Currant, and many other plants, yield a dehcate 

 perfume when touched. This essential oil usually resides 

 in small vesicles on the under side of the leaf; which 

 fact is easily demonstrated, for on rubbing only the upper 

 side no fragrance \^ill be noticed. Of course, for exa- 

 mining the vesicles under the microscope, the under side 

 of a leaf not iTibbed must be used. — A magnifying power 

 of 30 to 60 diameters will be sufficient for vie\Ndng them 

 by reflected light. 



Pollen. — The common form of the pollen or farina of 

 flowers is spherical, with either a smooth, punctured or 

 spiny surface ; but the most interesting forms are the 

 square, cyhndrical, oval with attenuated extremities, and 

 the triangular with convex sides. Examples of these 

 forms, together with several modifications, may be pro- 

 cured from the plants mentioned in the list. The colour 

 of these bodies is usually yellow or red, sometimes blue, 

 never green. In the microscope, poUen is best viewed by 

 reflected light, employing a silver cup or speculum. — 

 Magnifving power 30 to 100 diameters. 



The pollen of the Passion-flower is very curious, and 

 if immersed in very diluted sulphuric acid opens and dis- 

 perses the grains. This obsers-ation of course must be 

 made with transmitted light. 



